The present invention relates to a semiconductor device comprising a semiconductor substrate where a semiconductor element and a through electrode are formed, and a lid member attached to the semiconductor substrate, and also relates to a module for optical devices, and a manufacturing method of the semiconductor device.
Conventionally, a package of CCD image sensor, CMOS image sensor or the like is used as a semiconductor device, and a sensor module such as a CCD image sensor, a CMOS image sensor or the like is used as a module for optical devices.
FIG. 1 is a cross sectional view showing the structure of a conventional semiconductor device. A light receiving element 113 is formed in one surface (front surface) of a semiconductor substrate 111 of the semiconductor device, and a micro-lens part 114 is formed on the light receiving element 113.
The other surface (rear surface) of the semiconductor substrate 111 is bonded (die-bonded) to the internal bottom surface of a box-shaped container 115 made of ceramic or synthetic resin with an adhesive 117 (die-bonding resin). The opening of the box-shaped container 115 is sealed by attaching a glass lid 112 with an adhesive 119, so the light receiving element 113 and micro-lens part 114 in the box-shaped container 115 are protected from the external environment. Moreover, an electrode pad 109 (bonding pad) mounted on the front surface of the semiconductor substrate 111 and an electrode lead 116 drawn out from the inside of the box-shaped container 115 are electrically connected with a bonding wire 118.
FIG. 2 is a cross sectional view showing the structure of the conventional module for optical devices. The module for optical devices shown in FIG. 2 comprises lenses 123, a cylindrical optical path defining device 122 holding the lenses 123, and a wiring board 120. Further, the module for optical devices comprises the semiconductor substrate 111 having the light receiving element 113, micro-lens part 114 and electrode pad 109. The rear surface of the semiconductor substrate 111 is die-bonded onto the wiring board 120 with the adhesive 117, and the electrode pad 109 is electrically connected through the bonding wire 118 to a conductor wiring 121 provided on the wiring board 120.
One opening of the optical path defining device 122 is sealed by the glass lid 112 positioned to face the lens 123 and an adhesive 119, and the other opening is sealed by the wiring board 120 and an adhesive (not shown), so the light receiving element 113 and micro-lens part 114 are protected from the external environment. Before sealing the optical path defining device 122, it is necessary to protect the light receiving element 113 and micro-lens part 114 by other means.
The above-mentioned semiconductor device and module for optical devices require a space for connecting the electrode pad 109 to the electrode lead 116 or the conductor wiring 121 by using the bonding wire 118. Moreover, the bonding wire 118, electrode pad 109, etc. cannot be arranged on the light receiving element 113 or the micro-lens part 114 because the light receiving element 113 is blocked from light. As a result, it is difficult to reduce the sizes of the semiconductor device and the module for optical devices.
Therefore, in recent years, there were proposals to reduce the size of a semiconductor device or a module for optical devices by forming a through electrode passing through a semiconductor substrate from the front surface to the rear surface and forming a wiring line and a mounting terminal on the rear surface of the semiconductor substrate (see Japanese Patent Applications Laid Open Nos. 2001-351997 and 2002-94082).
FIGS. 3A and 3B are cross sectional views showing the structure of another conventional semiconductor device. The semiconductor device shown in FIG. 3A comprises a semiconductor substrate 111 where a light receiving element 113 and a micro-lens part 114 are formed. However, through electrodes 124 extending from the front surface to the rear surface of the semiconductor substrate 111 are formed, and a rear surface wiring 125 and solder balls 126 which are mounting terminals are formed on the rear surface of the semiconductor substrate 111. The through electrode 124 and the solder ball 126 are electrically connected with the rear surface wiring 125.
Further, a glass lid 112 is attached to the semiconductor substrate 111 so that the semiconductor substrate 111 and the glass lid 112 are substantially parallel to each other with an appropriate distance therebetween. In this case, for example, an adhesive part 127 made of an adhesive paste is printed on the front surface of the semiconductor substrate 111, the glass lid 112 is placed on the printed adhesive part 127, and then the adhesive part 127 is hardened by heat treatment. The hardened adhesive part 127 fastens the glass lid 112 to the semiconductor substrate 111 and supports it.
Such an adhesive part 127 is provided on the peripheral portion of the front surface of the semiconductor substrate 111 by avoiding the light receiving element 113 and micro-lens part 114. However, if the adhesive part 127 is formed by using an adhesive having a light transmitting property (for example, a transparent resin or low-melt point glass), the adhesive part 127 may be formed on the front surface of the semiconductor substrate 111, including the surface over the light receiving element 113 and micro-lens part 114. The space between the semiconductor substrate 111 and the glass lid 112 is sealed by the adhesive part 127, and the light receiving element 113 and micro-lens part 114 are protected from the external environment.
However, the adhesive part 127 of the conventional semiconductor device had a low hardness before hardened, and therefore as shown in FIG. 3B, the glass lid 112 sometimes sank into the adhesive part 127, decreased the distance between the glass lid 112 and the semiconductor substrate 111, and came into contact with the micro-lens part 114, light receiving element 113, etc. In this case, there was a problem that the micro-lens part 114 or the light receiving element 113 was damaged.
Moreover, the glass lid 112 sometimes tilted due to sinking of the glass lid 112 into the adhesive part 127. In this case, there was a problem that the light incident through the glass lid 112 could not be accurately received by the light receiving element 113.
For the above-mentioned problems, it was considered to form the adhesive part 127 in advance by using an adhesive with high hardness so as to prevent the glass lid 112 from sinking into the adhesive part 127. In this case, even when the glass lid 112 is mounted on the adhesive part 127, it is possible to prevent the glass lid 112 from sinking into the adhesive part 127. However, in order to seal the space between the glass lid 112 and semiconductor substrate 111 by securely bonding the adhesive part 127 and the glass lid 112 and semiconductor substrate 111, it is necessary to apply higher pressure to the glass lid 112 and the semiconductor substrate 111 compared to forming the adhesive part 127 by using an adhesive of low hardness, and therefore there is a possibility that the semiconductor substrate 111 will be damaged during the application of pressure.